Asymmetric battery having a semi-solid cathode and high energy density anode

ABSTRACT

Embodiments described herein relate generally to devices, systems and methods of producing high energy density batteries having a semi-solid cathode that is thicker than the anode. An electrochemical cell can include a positive electrode current collector, a negative electrode current collector and an ion-permeable membrane disposed between the positive electrode current collector and the negative electrode current collector. The ion-permeable membrane is spaced a first distance from the positive electrode current collector and at least partially defines a positive electroactive zone. The ion-permeable membrane is spaced a second distance from the negative electrode current collector and at least partially defines a negative electroactive zone. The second distance is less than the first distance. A semi-solid cathode that includes a suspension of an active material and a conductive material in a non-aqueous liquid electrolyte is disposed in the positive electroactive zone, and an anode is disposed in the negative electroactive zone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/228,259, filed Aug. 4, 2016, entitled “Asymmetric Battery Having ASemi-Solid Cathode And High Energy Density Anode,” which is acontinuation of U.S. patent application Ser. No. 14/202,606, filed Mar.10, 2014, now U.S. Pat. No. 9,437,864, entitled “Asymmetric BatteryHaving A Semi-Solid Cathode And High Energy Density Anode,” which claimspriority to and benefit of U.S. Provisional Application No. 61/787,372,filed Mar. 15, 2013 and entitled “Asymmetric Battery Having a Semi-solidCathode and High Energy Density Anode”, the entire disclosures of whichare hereby incorporated by reference herein in their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Grant NumberDE-AR0000102 awarded by the Department of Energy. The government hascertain rights in this invention.

BACKGROUND

Embodiments described herein relate generally to asymmetric batterieshaving high energy density anodes, and more particularly to devices,systems and methods of producing high energy density batteries having asemi-solid cathode that is thicker than the anode.

Batteries are typically constructed of solid electrodes, separators,electrolyte, and ancillary components such as, for example, packaging,thermal management, cell balancing, consolidation of electrical currentcarriers into terminals, and/or other such components. Theseconventional battery manufacturing methods generally involve complicatedand expensive manufacturing steps, such as casting the electrode, andare only suitable for electrodes of limited thickness, e.g., typicallyless than 100 μm. These known methods for producing electrodes oflimited thickness result in batteries with lower capacity, lower energydensity, and a high ratio of inactive components to active material.Said another way, the non-energy storage elements of the finisheddevice, that is the separator and current collector, comprise arelatively high fixed volume or mass fraction of the device, therebydecreasing the device's overall energy density.

Thus, it is an enduring goal of energy storage systems development tosimplify and reduce manufacturing cost, reduce inactive components inthe electrodes and finished batteries, and increase energy density andoverall performance.

SUMMARY

Embodiments described herein relate generally to devices, systems andmethods of producing high energy density batteries having a semi-solidcathode that is thicker than the anode. In some embodiments, anelectrochemical cell can include a positive electrode current collector,a negative electrode current collector and an ion-permeable membranedisposed between the positive electrode current collector and thenegative electrode current collector. The ion-permeable membrane isspaced a first distance from the positive electrode current collectorand at least partially defines a positive electroactive zone. Theion-permeable membrane is spaced a second distance from the negativeelectrode current collector and at least partially defines a negativeelectroactive zone. The second distance is less than the first distance.A semi-solid cathode that includes a suspension of an active materialand a conductive material in a non-aqueous liquid electrolyte isdisposed in the positive electroactive zone, and an anode is disposed inthe negative electroactive zone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an electrochemical cell accordingto an embodiment.

FIG. 2 is a schematic illustration of a symmetric electrochemical cell,according to an embodiment.

FIG. 3 is a schematic illustration of an asymmetric electrochemicalcell, according to an embodiment.

FIG. 4 is a schematic illustration of an asymmetric electrochemicalcell, according to an embodiment.

DETAILED DESCRIPTION

Embodiments described herein relate generally to devices, systems andmethods of producing high energy density batteries having a semi-solidcathode that is thicker than the anode. In some embodiments, anelectrochemical cell can include a positive electrode current collector,a negative electrode current collector and an ion-permeable membranedisposed between the positive electrode current collector and thenegative electrode current collector. The ion-permeable membrane isspaced a first distance from the positive electrode current collectorand at least partially defines a positive electroactive zone. Theion-permeable membrane is spaced a second distance from the negativeelectrode current collector and at least partially defines a negativeelectroactive zone. The second distance is less than the first distance.A semi-solid cathode that includes a suspension of an active materialand a conductive material in a non-aqueous liquid electrolyte isdisposed in the positive electroactive zone, and an anode is disposed inthe negative electroactive zone.

Consumer electronic batteries have gradually increased in energy densitywith the progress of lithium-ion battery technology. The stored energyor charge capacity of a manufactured battery is a function of: (1) theinherent charge capacity of the active material (mAh/g), (2) the volumeof the electrodes (cm³) (i.e., the product of the electrode thickness,electrode area, and number of layers (stacks)), and (3) the loading ofactive material in the electrode media (e.g., grams of active materialper cm³ of electrode media). Therefore, to enhance commercial appeal(e.g., increased energy density and decreased cost), it is generallydesirable to increase the areal charge capacity (mAh/cm²) The arealcharge capacity can be increased, for example, by utilizing activematerials that have a higher inherent charge capacity, increasingrelative percentage of active charge storing material (i.e., “loading”)in the overall electrode formulation, and/or increasing the relativepercentage of electrode material used in any given battery form factor.Said another way, increasing the ratio of active charge storingcomponents (e.g., the electrodes) to inactive components (e.g., theseparators and current collectors), increases the overall energy densityof the battery by eliminating, or reducing components that are notcontributing to the overall performance of the battery. One way toaccomplish increasing the areal charge capacity, and therefore reducingthe relative percentage of inactive components, is by increasing thethickness of the electrodes.

In some embodiments, higher energy densities and capacities can beachieved by, for example, improvements in the materials used in theanode and or cathode, and/or increasing the thickness of the anodecathode (i.e., higher ratio of active materials to inactive materials).One of the latest materials used in the anode for consumer electronicsis, for example, silicon (Si), tin (Sn), silicon alloys, or tin alloysdue to their high capacity and low voltage. Typically, this highcapacity active material is mixed with graphite due to its high firstcharge capacity and related first charge irreversible capacity. Siliconhas a first charge theoretical capacity of 4,200 mAh/g and anirreversible capacity of more than 300 mAh/g. Therefore, typical anodesthat utilize Si contain a mixture of silicon and graphite in order toreduce the irreversible capacity. In addition, silicon undergoes a verylarge volume change during lithium insertion causing the volume of thematerial to grow by more than 300%. To limit this large volumetricexpansion, current high capacity anodes utilize between 10-20% siliconin the anode mixture resulting in anodes with overall capacity of about700 to about 4,200 mAh/g.

Conventional cathode compositions have capacities of approximately150-200 mAh/g and cannot be made thicker than 200 μm becauseconventional electrodes manufactured using the high speed roll-to-rollcalendering process tend to delaminate from the flat current collectorsif they are made thicker than about 200 μm. Additionally, thickerelectrodes have higher cell impedance, which reduces energy efficiency(e.g., as described in Yu et al “Effect of electrode parameters onLiFePO₄ cathodes”, J. Electrochem. Soc. Vol. 153, A835-A839 (2006)).Therefore, to match the high capacity anodes with the conventionalcathodes, current state-of-the-art batteries have focused on reducingthe thickness of the anode. For example, anodes having a thickness ofabout 40-50 μm and even thinner are being developed. Such thin coatingsof these anode materials begin to approach the thickness level of asingle graphite particle. The limitation of thickness and associatedloading density in conventional coating processes has preventeddevelopment of batteries that take full advantage of the high capacitythat is available in high energy anodes.

Semi-solid cathodes described herein can be made: (i) thicker (e.g.,greater than 200 μm—up to 2,000 μm or even greater) due to the reducedtortuosity and higher electronic conductivity of the semi-solidelectrode, (ii) with higher loadings of active materials, and (iii) witha simplified manufacturing process utilizing less equipment, therebydecreasing the volume, mass and cost contributions of inactivecomponents with respect to active components. Examples of semi-solidscathodes having a thickness greater that 200 μm without an adverseaffect on impedance, energy efficiency, energy density or capacity aredescribed in U.S. Provisional Patent Application No. 61/787,382 filedMar. 15, 2013, entitled “Semi-Solid Electrodes Having High. RateCapability,” the disclosure of which is hereby incorporated byreference. Examples of systems and methods that can be used forpreparing the semi-solid compositions and/or electrodes are described inU.S. patent application Ser. No. 13/832,861 filed Mar. 15, 2013,entitled “Electrochemical Slurry Compositions and Methods for Preparingthe Same,” the entire disclosure of which is hereby incorporated byreference.

Since the semi-solid cathodes can be much thicker than conventionalelectrodes (e.g., greater than 200 μm), and with higher loadingdensities, the semi-solid cathode can be more effectively paired withhigh energy anodes. Said another way, the thicker semi-solid cathodeenables active material loading densities that are three, four, five, ormore times higher than conventional coated electrodes. The thickersemi-solid cathodes with higher loading densities can be paired withanodes that utilize silicon, tin, or other high energy anode materialswithout having to maintain a thin anode and/or loading density. The highcapacity anodes can be made with conventional coating methods and havehigher loading density that approach the maximum active material loadingdensity of conventional electrodes that utilize binder and as a result,still be matched/balanced with the cathode. The pairing of thesemi-solid cathode with the high capacity anode can result in cells withvolumetric energy densities that are greater than 600 Wh/L or greater.In some embodiments, the anode can be a semi-solid anode made with highenergy anode materials in a similar fashion as described with respect tothe semi-solid cathode.

In some embodiments, the electrode materials described herein can be aflowable semi-solid or condensed liquid composition. A flowablesemi-solid electrode can include a suspension of an electrochemicallyactive material (anodic particles or particulates), and optionally anelectronically conductive material (e.g., carbon) in a non-aqueousliquid electrolyte. Said another way, the active electrode particles andconductive particles are co-suspended in an electrolyte to produce asemi-solid electrode. The anode includes a high energy anode materiale.g., silicon, tin, aluminum, titanium oxide or any other high capacitymaterial, alloys or combination thereof. In some embodiments, the anodecan be formed using a conventional coating/calendering process. In someembodiments, the anode can be a semi-solid anode that includes highenergy anodic particles and carbon (e.g. graphite) particlesco-suspended in an electrolyte to produce a semi-solid anode. Examplesof battery architectures utilizing semi-solid suspensions are describedin International Patent Publication No. WO 2012/024499, entitled“Stationary, Fluid Redox Electrode,” and International PatentPublication No. WO 2012/088442, entitled “Semi-Solid Filled Battery andMethod of Manufacture,” the entire disclosures of which are herebyincorporated by reference.

As used herein, the term “about” and “approximately” generally mean plusor minus 10% of the value stated, e.g., about 250 μm would include 225μm to 275 μm, about 1,000 μm would include 900 μm to 1,100 μm.

As used herein, the term “semi-solid” refers to a material that is amixture of liquid and solid phases, for example, such as particlesuspension, colloidal suspension, emulsion, gel, or micelle.

As used herein, the term “condensed ion-storing liquid” or “condensedliquid” refers to a liquid that is not merely a solvent, as in the caseof an aqueous flow cell semi-solid cathode, or anode, but rather, it isitself redox active. Of course, such a liquid form may also be dilutedby or mixed with another, non-redox active liquid that is a diluent orsolvent, including mixing with such a diluent to form a lower-meltingliquid phase, emulsion or micelles including the ion-storing liquid.

As used herein, the terms “activated carbon network” and “networkedcarbon” relate to a general qualitative state of an electrode. Forexample, an electrode with an activated carbon network (or networkedcarbon) such that the carbon particles within the electrode assume anindividual particle morphology and arrangement with respect to eachother that facilitates electrical contact and electrical conductivitybetween particles. Conversely, the terms “unactivated carbon network”and “unnetworked carbon” relate to an electrode wherein the carbonparticles either exist as individual particle islands or multi-particleagglomerate islands that may not be sufficiently connected to provideadequate electrical conduction through the electrode.

As used herein, the term “volumetric energy density” refers to theamount of energy (e.g., Wh) stored in an electrochemical cell per unitvolume (e.g., L) of the materials required for the electrochemical cellto operate such as, the electrodes, the separator, the electrolyte, andthe current collectors. Specifically, the materials used for packagingthe electrochemical cell are excluded from the calculation of volumetricenergy density.

In some embodiments, an electrochemical cell for storing energy includesa positive electrode current collector, a negative electrode currentcollector and an ion-permeable membrane disposed between the positiveelectrode current collector and the negative electrode currentcollector. The ion-permeable membrane is spaced a first distance fromthe positive electrode current collector and at least partially definesa positive electroactive zone. The ion-permeable membrane is spaced asecond distance from the negative electrode current collector and atleast partially defines a negative electroactive zone. The seconddistance is less than the first distance. A semi-solid cathode thatincludes a suspension of an active material and a conductive material ina non-aqueous liquid electrolyte is disposed in the positiveelectroactive zone, and an anode is disposed in the negativeelectroactive zone. In some embodiments, the anode can be a semi-solidanode that includes a suspension of a high capacity active material anda carbon material in a non-aqueous liquid electrolyte.

In some embodiments, the anode includes at least one high capacity anodematerial selected from silicon, bismuth, boron, gallium, indium, zinc,tin, antimony, aluminum, titanium oxide, molybdenum, germanium,manganese, niobium, vanadium, tantalum, iron, copper, gold, platinum,chromium, nickel, cobalt, zirconium, yttrium, molybdenum oxide,germanium oxide, silicon oxide, silicon carbide, any other high capacitymaterials or alloys thereof, and any combination thereof.

In some embodiments, the first distance is at least about 250 μm. Insome embodiments, the first distance is about 300 μm, about 350 μm,about 400 μm, about 450 μm, about 500 μm, about 600 μm, about 700 μm,about 800 μm, about 900 μm, about 1,000 μm, about 1,500 μm, and up toabout 2,000 μm, inclusive of all thicknesses therebetween.

In some embodiments, the first distance is in the range of about 250 μmto about 2,000 μm, about 300 μm to about 2,000 μm, about 350 μm to about2,000 μm, 400 μm to about 2,000 μm, about 450 μm to about 2,000 μm,about 500 to about 2,000 μm, about 250 μm to about 1,500 μm, about 300μm to about 1,500 μm, about 350 μm to about 1,500 μm, about 400 μm toabout 1,500 μm, about 450 μm to about 1,500 μm, about 500 to about 1,500μm, about 250 μm to about 1,000 μm, about 300 μm to about 1,000 μm,about 350 μm to about 1,000 μm, about 400 μm to about 1,000 μm, about450 μm to 1,000 μm, about 500 μm to about 1,000 μm, about 250 μm toabout 750 μm, about 300 μm to about 750 μm, about 350 μm to about 750μm, about 400 μm to about 750 μm, about 450 μm to about 750 μm, about500 μm to about 750 μm, about 250 μm to about 700 μm, about 300 μm toabout 700 μm, about 350 μm to about 700 μm, about 400 μm to about 700μm, about 450 μm to about 700 μm, about 500 μm to about 700 μm, about250 μm to about 650 μm, about 300 μm to about 650 μm, about 350 μm toabout 650 μm, about 400 μm to about 650 μm, about 450 μm to about 650μm, about 500 μm to about 650 μm, about 250 μm to about 600 μm, about300 μm to about 600 μm, about 350 μm to about 600 μm, about 400 μm toabout 600 μm, about 450 μm to about 600 μm, about 500 μm to about 600μm, about 250 μm to about 550 μm, about 300 μm to about 550 μm, about350 μm to about 550 μm, about 400 μm to about 550 μm, about 450 μm toabout 550 μm, or about 500 μm to about 550 μm, inclusive of all rangesor any other distance therebetween.

In some embodiments, the second distance is in the range of about 30 μmto about 200 μm, about 40 μm to about 200 μm, about 50 μm to about 200μm, about 60 μm to about 200 μm, about 70 μm to about 200 μm, about 100μm to about 200 μm, about 150 μm to about 200 μm, about 200 μm to about300 μm, about 200 μm to about 400 μm, about 200 μm to about 500 μm,inclusive of all ranges or any other distance therebetween.

In some embodiments, the anode can include about 66 wt %-70 wt % Si,about 15 wt %-22 wt % Co, and about 4 wt %-12 wt % C. In someembodiments, the anode can include about 70 wt % Si, about 15 wt %-20 wt% Ni and about 10 wt %-15 wt % C. In some embodiments, the anode caninclude about 70 wt % Si, about 15 wt % Fe and about 15 wt % C. In someembodiments, the anode can include about 70 wt % Si, about 20 wt % Ti,and about 10 wt % C. In some embodiments, the anode can include about 70wt % Si, about 15 wt % Mo and about 15 wt % C. In some embodiments, theanode can include about 70 wt % Si, 15 wt % Co, 5 wt % Ni and about 10wt % C. In some embodiments, the anode can include about 70 wt % Si,about 10 wt % Co, about 10 wt % Ni and about 10 wt % C. In someembodiments, the anode can include about 70 wt % Si, about 5 wt % Co,about 15 wt % Ni and about 10 wt % C. In some embodiments, the anode caninclude about 70 wt % Si, about 5 wt % Fe, about 10 wt % Ni and about 15wt % C. In some embodiments, the anode can include about 70 wt % Si, 10wt % Co and about 5 wt % Ni. In some embodiments, the anode can includeabout 74 wt % Si, 2 wt % Sn and about 24 wt % Co. In some embodiments,the anode can include about 73 wt % Si, about 2 wt % Sn and about 25 wt% Ni. In some embodiments, the anode can include about 70 wt % Si, 10 wt% Fe, about 10 wt % Ti and about 10 wt % Co. In some embodiments, theanode can include about 70 wt % Si, about 15 wt % Fe, about 5 wt % Tiand about 10 wt % C. In some embodiments, the anode can include about74.67 wt % Si, 16 wt % Fe, 5.33 wt % Ti and 4 wt % C. In someembodiments, the anode can include about 55 wt % Si, 29.3 wt % Al andabout 15.7 wt % Fe. In some embodiments, the anode can include about 70wt % Si, about 20 wt % C from a precursor and about 10 wt % graphite byweight. In some embodiments, the anode can include about 55 wt % Si,about 29.3 wt % Al and about 15.7 wt % Fe. In some embodiments, theanode can include about 60-62 wt % Si, about 16-20 wt % Al, about 12-14wt % Fe, and about 8% Ti. In some embodiments, the anode can includeabout 50 wt % Sn, about 27.3 wt %-35.1 wt % Co, about 5 wt %-15 wt % Ti,and about 7.7 wt %-9.9 wt % C. In some embodiments, the anode caninclude about 50 wt % Sn, about 39-42.3 wt % Co, and about 7.7-11 wt %C. In some embodiments, the anode can include about 35-70 mole % Si,about 1-45 mole % Al, about 5-25 mole % transition metal, about 1-15mole % Sn, about 2-15 mole % yttrium, a lanthanide element, an actinideelement or a combination thereof.

In some embodiments, the anode can include a tin metal alloy such as,for example, a Sn—Co—C, a Sn—Fe—C, a Sn—Mg—C, or a La—Ni—Sn alloy. Insome embodiments, the anode can include an amorphous oxide such as, forexample, SnO or SiO amorphous oxide. In some embodiments, the anode caninclude a glassy anode such as, for example, a Sn—Si—Al—B—O, aSn—Sb—S—O, a SnO₂—P₂O₅, or a SnO—B₂O₃—P₂O₅—Al₂O₃ anode. In someembodiments, the anode can include a metal oxide such as, for example, aCoO, a SnO₂, or a V₂O₅. In some embodiments, the anode can include ametal nitride such as, for example, Li₃N or Li₂.6CoO.4N.

In some embodiments, the anode can be single layer anode that includesall components of the anode (e.g., active material, conductive material,electrolyte, and high capacity layer) mixed together in the layer. Insome embodiments, the anode can include a multi-layer structure, forexample, a multiple layers of high capacity anode materials combinedwith carbon materials.

In some embodiments, an electrochemical cell includes a semi-solidcathode including a suspension of an active material and a conductivematerial in a non-aqueous liquid electrolyte, the semi-solid cathodehaving a capacity of about 150-200 mAh/g and a thickness in the range ofabout 250 μm to about 2,000 μm, and an anode that has a capacity in therange of about 700-1,200 mAh/g and a thickness the range of about 30 μmto about 600 μm. The anode and semi-solid cathode are separated by aseparator disposed therebetween.

In some embodiments, the anode includes an anode active materialselected from lithium metal, carbon, lithium-intercalated carbon,lithium nitrides, lithium alloys and lithium alloy forming compounds ofsilicon, bismuth, boron, gallium, indium, zinc, tin, antimony, aluminum,titanium oxide, molybdenum, germanium, manganese, niobium, vanadium,tantalum, gold, platinum, iron, copper, chromium, nickel, cobalt,zirconium, yttrium, molybdenum oxide, germanium oxide, silicon oxide,silicon carbide, any other high capacity materials or alloys thereof,and any other combination thereof. In some embodiments, the anode activematerial can include silicon and/or alloys thereof. In some embodiments,anode active material can include tin and/or alloys thereof.

In some embodiments, the thickness of the cathode can be in the range ofabout 2 times to about 6 times the thickness of the anode. In someembodiments, the thickness of the cathode can be in the range of about 2to about 5, about 2 to about 4, about 2 to about 3, about 3 to about 6,about 4 to about 6, or about 5 to about 6 times the thickness of theanode.

In some embodiments, a semi-solid cathode can include about 20% to about75% by volume of an active material. In some embodiments, a semi-solidcathode can include about 40% to about 75% by volume, or 60% to about75% by volume of an active material.

In some embodiments, a semi-solid cathode can include about 0.5% toabout 25% by volume of a conductive material. In some embodiments, asemi-solid cathode can include about 1.0% to about 6% by volume of aconductive material.

In some embodiments, a semi-solid cathode can include about 25% to about70% by volume of an electrolyte. In some embodiments, a semi-solidcathode can include about 30% to about 50%, or about 20% to about 40% byvolume of an electrolyte.

In some embodiments, the anode is a solid anode formed on a negativeelectrode current collector. In some embodiments, the anode is asemi-solid anode that includes about 50% to about 75% by volume of acarbonaceous active material, about 1% to about 10% by volume of a highenergy capacity anode material, about 0.5% to about 2% by volume of aconductive material, and about 20% to about 40% by volume of annon-aqueous liquid electrolyte. In some embodiments, the high capacityanode material includes at least one high capacity anode materialselected from silicon, silicon alloys, tin, tin alloys, aluminum andtitanium oxide.

In some embodiments, a semi-solid anode can include about 0% to about75% by volume of an active material. In some embodiments, a semi-solidanode can include about 40% to about 75% by volume, or about 50% toabout 75% by volume of an active material.

In some embodiments, a semi-solid anode can include about 0% to about75% by volume of a high energy capacity material. In some embodiments, asemi-solid anode can include about 1% to about 30% by volume, about 1%to about 20% by volume, about 1% to about 10% by volume, or about 1% toabout 5% of a high energy capacity material.

In some embodiments, a semi-solid anode can include about 0% to about10% by volume of a conductive material. In some embodiments, asemi-solid anode can include about 1% to about 6%, or about 0.5% toabout 2% by volume of a conductive material.

In some embodiments, a semi-solid anode can include about 10% to about70% by volume of an electrolyte. In some embodiments, a semi-solid anodecan include about 30% to about 50%, or about 20% to about 40% by volumeof an electrolyte.

In some embodiments, an electrochemical cell including a semi-solidcathode and a high energy anode can have a volumetric energy densitythat is greater than about 600 Wh/L, greater than about 700 Wh/L,greater than about 800 Wh/L, greater than about 900 Wh/L, greater thanabout 1,000 Wh/L, greater than about 1,100 Wh/L, and up to about 1,200Wh/L.

In some embodiments, an electrochemical cell can include an anode, asemi-solid cathode material that includes about 60% to about 80% byweight of an active material, about 1% to about 6% by weight of aconductive material, and about 20% to about 40% by weight of anon-aqueous liquid electrolyte. A separator is disposed between theanode and the semi-solid cathode such that the thickness of the cathodeis at least about two times the thickness of the anode. In someembodiments, the thickness of the cathode is at least about three timesthe thickness of the anode. In some embodiments, the thickness of thecathode is at least about four times the thickness of the anode. In someembodiments, the thickness of the cathode is at least about five timesthe thickness of the anode.

In some embodiments, an electrochemical cell includes a semi-solidcathode that can include about 60% to about 80% by weight of an activematerial, about 1% to about 6% by weight of a conductive material, andabout 20% to about 40% by weight of a non-aqueous liquid electrolyte.The semi solid cathode can have a thickness in the range of about 250 μmto about 2,000 μm. The electrochemical cell also includes an anode thatcan include a high charge capacity material and can have an overallcapacity in the range of about 700 mAh/g to about 1,200 mAh/g. The anodecan have a thickness in the range of about 20% to about 25% of thecathode thickness. The anode and semi-solid cathode are separated by aseparator disposed therebetween.

In some embodiments, a method of manufacturing an electrochemical cellincludes transferring an anode semi-solid suspension to a negativeelectroactive zone defined at least in part by an anode currentcollector and an ion-permeable membrane spaced apart from the anodecollector. The method also includes transferring a cathode semi-solidsuspension to a positive electroactive zone defined at least in part bya cathode current collector and an ion-permeable membrane spaced apartfrom the cathode current collector. The transferring of the anodesemi-solid suspension to the anode compartment and the cathodesemi-solid suspension to the cathode compartment can be performed suchthat a difference between a minimum distance and a maximum distancebetween the anode current collector and the ion permeable membrane ismaintained within a predetermined tolerance. Furthermore, the thicknessof positive electroactive zone is substantially greater than thethickness of the negative electroactive zone. In some embodiments, thepositive electroactive zone can be about two fold, three fold, four foldor five fold thicker than the negative electroactive zone. The methodfurther includes sealing the negative electroactive zone and thepositive electroactive zone.

In some embodiments, a method of manufacturing an electrochemical cellincludes disposing an injection nozzle in an electrode that is defined,at least in part by a current collector and an ion-permeable membrane. Asemi-solid cathode material transferred to the electroactive zonethrough the injection nozzle. The injection nozzle is then withdrawnfrom the electrode compartment during at least a portion of thetransferring and then the electrode compartment is sealed.

FIG. 1 shows a schematic illustration of an electrochemical cell 100 forstoring energy with high capacity. The electrochemical cell 100 includesa positive current collector 110, a negative current collector 120 and aseparator 130 disposed between the positive current collector 110 andthe negative current collector 120. The positive current collector 110is spaced a first distance t₁ from the separator 130 and at leastpartially defines a positive electroactive zone. The negative currentcollector 120 is spaced a second distance t₂ from the separator 130 andat least partially defines a negative electroactive zone. The firstdistance is substantially greater than t₂. A semi-solid cathode 140 isdisposed in the positive electroactive zone and an anode 150 is disposedin the negative electroactive zone, such that the first distance t₁defines thickness of the cathode 140 and the second distance t₂ definesthe thickness of the anode 150.

The positive current collector 110 and the negative current collector120 can be any current collectors that are electronically conductive andare electrochemically inactive under the operation conditions of thecell. Typical current collectors for lithium cells include copper,aluminum, or titanium for the negative current collector and aluminumfor the positive current collector, in the form of sheets or mesh, orany combination thereof.

Current collector materials can be selected to be stable at theoperating potentials of the positive and negative electrodes of theelectrochemical cell 100. For example, in non-aqueous lithium systems,the positive current collector can include aluminum, or aluminum coatedwith conductive material that does not electrochemically dissolve atoperating potentials of 2.5-5.0V with respect to Li/Li⁺. Such materialsinclude platinum, gold, nickel, conductive metal oxides such as vanadiumoxide, and carbon. The negative current collector can include copper orother metals that do not form alloys or intermetallic compounds withlithium, carbon, and/or coatings comprising such materials disposed onanother conductor.

The separator 130 can be any suitable separator that acts as anion-permeable membrane, i.e. allows exchange of ions while maintainingphysical separation of the cathode 140 and anode 150 compositions. Forexample, the separator 130 can be any conventional membrane that iscapable of ion transport. In some embodiments, the separator 130 is aliquid impermeable membrane that permits the transport of ionstherethrough, namely a solid or gel ionic conductor. In some embodimentsthe separator 130 is a porous polymer membrane infused with a liquidelectrolyte that allows for the shuttling of ions between the cathode140 and anode 150 electroactive materials, while preventing the transferof electrons. In some embodiments, the separator 130 is a microporousmembrane that prevents particles forming the positive and negativeelectrode compositions from crossing the membrane. For example, themembrane materials can be selected from polyethyleneoxide (PEO) polymerin which a lithium salt is complexed to provide lithium conductivity, orNation™ membranes which are proton conductors. For example, PEO basedelectrolytes can be used as the membrane, which is pinhole-free and asolid ionic conductor, optionally stabilized with other membranes suchas glass fiber separators as supporting layers. PEO can also be used asa slurry stabilizer, dispersant, etc. in the positive or negative redoxcompositions. PEO is stable in contact with typical alkylcarbonate-based electrolytes. This can be especially useful inphosphate-based cell chemistries with cell potential at the positiveelectrode that is less than about 3.6 V with respect to Li metal. Theoperating temperature of the redox cell can be elevated as necessary toimprove the ionic conductivity of the membrane.

The cathode 140 can be a semi-solid stationary cathode or a semi-solidflowable cathode, for example of the type used in redox flow cells. Thecathode 140 can include an active material such as a lithium bearingcompound as described in further detail below. The cathode 140 can alsoinclude a conductive material such as, for example, graphite, carbonpowder, pyrolytic carbon, carbon black, carbon fibers, carbonmicrofibers, carbon nanotubes (CNTs), single walled CNTs, multi walledCNTs, fullerene carbons including “bucky ball,” graphene sheets and/oraggregate of graphene sheets, any other conductive material, alloys orcombination thereof. The cathode 140 can also include a non-aqueousliquid electrolyte as described in further detail below.

In some embodiments, the semi-solid cathode 140 can include about20%-75% by volume of an active material, about 0.5%-25% by volume of aconductive material and about 25%-70% by volume of an electrolyte. Insome embodiments, the semi-solid cathode 140 can include about 60% toabout 80% by weight of an active material, about 1% to about 6% byweight of a conductive material, and about 20% to about 40% by weight ofa non-aqueous liquid electrolyte.

In some embodiments, the thickness t₁ of the cathode 140 can be in therange of about two times to about six times the thickness t₂ of theanode 150. In some embodiments, the thickness t₁ of the cathode 140 canbe about two times the thickness t₂ of the anode 150. In someembodiments, the thickness t₁ of the cathode 140 can be about threetimes the thickness t₂ of the anode 150. In some embodiments, thethickness t₁ of the cathode 140 can be about four times the thickness t₂of the anode 150. In some embodiments, the thickness t₁ of the cathode140 can be about five times the thickness t₂ of the anode 150. In someembodiments, the thickness t₁ of the cathode 140 can be about six timesthe thickness t₂ of the anode 150.

The anode 150 can be a conventional anode, e.g., formed through aconventional coating and calendering process. In some embodiments, theanode 150 can be a semi-solid stationary anode. In some embodiments, theanode 150 can be a semi-solid flowable anode, e.g., of the type used inredox flow cells. The anode 150 is a high capacity anode that includeshigh capacity active materials, e.g., silicon, bismuth, boron, gallium,indium, zinc, tin, antimony, aluminum, titanium oxide, molybdenum,germanium, manganese, niobium, vanadium, tantalum, iron, copper,chromium, nickel, cobalt, zirconium, yttrium, molybdenum oxide,germanium oxide, silicon oxide, silicon carbide, any other high capacitymaterials or alloys thereof, or any other combination thereof.

The anode 150 can also include a carbonaceous material such as, e.g.,graphite, carbon powder, pyrolytic carbon, carbon black, carbon fibers,carbon microfibers, carbon nanotubes (CNTs), single walled CNTs, multiwalled CNTs, fullerene carbons including “bucky balls”, graphene sheetsand/or aggregate of graphene sheets, any other carbonaceous material orcombination thereof. In some embodiments, the anode 150 can also includea non-aqueous liquid electrolyte as described in further detail below.

In some embodiments, the thickness t₂ of anode 150 can be about 20-25%of the thickness t₁ of the cathode 140. In some embodiments, thethickness t₂ of the anode 150 can be in the range of about 30 μm toabout 600 μm, about 40 μm to about 600 μm, about 50 μm to about 600 μm,about 70 μm to about 600 μm, about 100 μm to about 600 μm, about 150 μmto about 600 μm, about 200 μm to about 600 μm, about 50 μm to about 500μm, about 100 μm to about 500 μm, about 150 μm to about 500 μm, about200 μm to about 500 μm, about 100 μm to about 400 μm, about 150 μm toabout 400 μm, about 200 μm to about 400 μm, about 100 μm to about 300μm, about 150 μm to about 300 μm, about 200 μm to about 300 μm, about 30μm to about 200 μm, about 40 μm to about 200 μm, about 50 μm to about200 μm, about 60 μm to about 200 μm, about 70 μm to about 200 μm, about100 μm to about 200 μm, about 150 μm to about 200 μm, about 200 μm,about 300 μm, inclusive of any other thickness or thickness rangetherebetween.

In some embodiments, the cathode 140 and the anode 150 can both includesemi-solid suspensions. In such embodiments, the cathode 140 and theanode 150 can include active materials and optionally conductivematerials in particulate form suspended in a non-aqueous liquidelectrolyte. In some embodiments, the cathode 140 and/or anode 150particles have an effective diameter of at least about 1 μm. In someembodiments, the cathode 140 and/or anode 150 particles have aneffective diameter between about 1 μm and about 10 μm. In otherembodiments, the cathode 140 and/or anode 150 particles have aneffective diameter of at least about 10 μm or more.

In some embodiments, a redox mediator is used to improve the chargetransfer within the semi-solid suspension. In some embodiments, theredox mediator is based on Fe²⁺ or V²⁺, V³⁺, or V⁴⁺. In someembodiments, the redox mediator is ferrocene.

In some embodiments, the conductive particles have shapes, which mayinclude spheres, platelets, or rods to optimize solids packing fraction,increase the semi-solid's net electronic conductivity, and improverheological behavior of semi-solids. Low aspect or substantiallyequiaxed particles tend to flow well, however, they tend to have a lowpacking density.

In some embodiments, the particles have a plurality of sizes so as toincrease packing fraction by placing smaller particles in theinterstices of the larger particles. In particular, the particle sizedistribution can be biomodal, in which the average particle size of thelarger particle mode is at least 5 times larger than average particlesize of the smaller particle mode. The mixture of large and smallparticles improves flow of the material during cell loading andincreases solid volume fraction and packing density the loaded cell.

In some embodiments, the nature of cathode 140 and/or anode 150semi-solid suspension can be modified prior to and subsequent to fillingof the negative electroactive zone and the positive electroactive zoneto facilitate flow during loading and packing density in the loadedcell.

In some embodiments, the particle suspension is initially stabilized byrepulsive interparticle steric forces that arise from surfactantmolecules. After the particle suspension is loaded into the positiveelectroactive zone and/or the negative electroactive zone, chemical orheat treatments can cause these surface molecules to collapse orevaporate and promote densification. In some embodiments, thesuspension's steric forces are modified intermittently during loading.

For example, the particle suspension can be initially stabilized byrepulsive interparticle electrostatic double layer forces to decreaseviscosity. The repulsive force reduces interparticle attraction andreduces agglomeration. After the particle suspension is loaded into thepositive electroactive zone and/or negative electroactive zone, thesurface of the particles can be further modified to reduce interparticlerepulsive forces and thereby promote particle attraction and packing.For example, ionic solutions such as salt solutions can be added to thesuspension to reduce the repulsive forces and promote aggregation anddensification so as to produce increased solids fraction loading afterfilling of the electroactive zones. In some embodiments, salt is addedintermittently during suspension loading to increase density inincremental layers.

In some embodiments, the positive and/or negative electroactive zonesare loaded with a particle suspension that is stabilized by repulsiveforces between particles induced by an electrostatic double layer orshort-range steric forces due to added surfactants or dispersants.Following loading, the particle suspension is aggregated and densifiedby increasing the salt concentration of the suspension. In someembodiments, the salt that is added to is a salt of a working ion forthe battery (e.g., a lithium salt for a lithium ion battery) and uponbeing added, causes the liquid phase to become an ion-conducting,electrolyte (e.g., for a lithium rechargeable battery, may be one ormore alkyl carbonates, or one or more ionic liquids). Upon increasingthe salt concentration, the electrical double layer causing repulsionbetween the particles is “collapsed”, and attractive interactions causethe particle to floc, aggregate, consolidate, or otherwise density. Thisallows the electrode of the battery to be formed from the suspensionwhile it has a low viscosity, for example, by pouring, injection, orpumping into the positive and/or negative electroactive zones that canform a net-shaped electrode, and then allows particles within thesuspension to be consolidated for improved electrical conduction, higherpacking density and longer shelf life.

In some embodiments, the flowable cathode 140 and/or anode 150semi-solid suspension is caused to become non-flowable by “fixing”. Insome embodiments, fixing can be performed by the action ofphotopolymerization. In some embodiments, fixing is performed by actionof electromagnetic radiation with wavelengths that are transmitted bythe unfilled positive and/or negative electroactive zones of theelectrochemical cell 100. In some embodiments, one or more additives areadded to the semi-solid suspensions to facilitate fixing.

In some embodiments, the injectable and flowable cathode 140 and/oranode 150 semi-solid is caused to become non-flowable by “plasticizing”.In some embodiments, the rheological properties of the injectable andflowable semi-solid suspension are modified by the addition of athinner, a thickener, and/or a plasticizing agent. In some embodiments,these agents promote processability and help retain compositionaluniformity of the semi-solid under flowing conditions and positive andnegative electroactive zone filling operations. In some embodiments, oneor more additives are added to the flowable semi-solid suspension toadjust its flow properties to accommodate processing, requirements.

Semi-Solid Composition

In some embodiments, the cathode 140 and in some embodiments, the anode150 semi-solids provide a means to produce a substance that functionscollectively as an ion-storage/ion-source, electron conductor, and ionicconductor in a single medium that acts as a working electrode.

The cathode 140 and/or anode 150 semi-solid ion-storing redoxcomposition as described herein can have, when taken in moles per liter(molarity), at least 10M concentration of redox species. In someembodiments, the cathode 140 and/or the anode 150 semi-solidsion-storing redox composition can have at least 12M, at least 15M, or atleast 20M. The electrochemically active material can be an ion storagematerial and or any other compound or ion complex that is capable ofundergoing Faradaic reaction in order to store energy. The electroactivematerial can also be a multiphase material including the above describedredox-active solid mixed with a non-redox-active phase, includingsolid-liquid suspensions, or liquid-liquid multiphase mixtures,including micelles or emulsions having a liquid ion-storage materialintimately mixed with a supporting liquid phase. Systems that utilizevarious working ions can include aqueous systems in which Li⁺, Na⁺, orother alkali ions are the working ions, even alkaline earth working ionssuch as Ca²⁺, Mg²⁺, or Al³⁺. In each of these instances, a negativeelectrode storage material and a positive electrode storage material maybe required, the negative electrode storing the working ion of interestat a lower absolute electrical potential than the positive electrode.The cell voltage can be determined approximately by the difference inion-storage potentials of the two ion-storage electrode materials.

Systems employing both negative and positive ion-storage materials areparticularly advantageous because there are no additionalelectrochemical byproducts in the cell. Both the positive and negativeelectrode materials are insoluble in the electrolyte and the electrolytedoes not become contaminated with electrochemical composition products.In addition, systems employing both negative and positive lithiumion-storage materials are particularly advantageous when usingnon-aqueous electrochemical compositions.

In some embodiments, the semi-solid ion-storing redox compositionsinclude materials proven to work in conventional, solid lithium-ionbatteries. In some embodiments, the positive semi-solid electroactivematerial contains lithium positive electroactive materials and thelithium cations are shuttled between the negative electrode and positiveelectrode, intercalating into solid, host particles suspended in aliquid electrolyte.

In some embodiments, at least one of the semi-solid cathode 140 and/oranode 150 includes a condensed ion-storing liquid of a redox-activecompound, which may be organic or inorganic, and includes but is notlimited to lithium metal, sodium metal, lithium-metal gallium and indiumalloys with or without dissolved lithium, molten transition metalchlorides, thionyl chloride, and the like, or redox polymers andorganics that can be liquid under the operating conditions of thebattery. Such a liquid form may also be diluted by or mixed withanother, non-redox-active liquid that is a diluent or solvent, includingmixing with such diluents to form a lower-melting liquid phase. In someembodiments, the redox-active component can comprise, by mass, at least10% of the total mass of the electrolyte. In other embodiments, theredox-active component will comprise, by mass, between approximately 10%and 25% of the total mass of the electrolyte. In some embodiments, theredox-active component will comprise by mass, at least 25% or more ofthe total mass of the electrolyte.

In some embodiments, the redox-active electrode material, whether usedas a semi-solid or a condensed liquid format as defined above, comprisesan organic redox compound that stores the working ion of interest at apotential useful for either the positive or negative electrode of abattery. Such organic redox-active storage materials include “p”-dopedconductive polymers such as polyaniline or polyacetylene basedmaterials, polynitroxide or organic radical electrodes such as thosedescribed in: H. Nishide et al., Electrochim. Acta, 50, 827-831, (2004),and K. Nakahara, et al., Chem. Phys. Lett., 359, 351-354 (2002)),carbonyl based organics, and oxocarbons and carboxylate, includingcompounds such as Li₂C₆O₆, Li₂C₈H₄O₄, and Li₂C₆H₄O₄ (see for example M.Armand et al., Nature Materials, DOI: 10.1038/nmat2372) and organosulfurcompounds.

In some embodiments, organic redox compounds that are electronicallyinsulating are used. In some instance, the redox compounds are in acondensed liquid phase such as liquid or flowable polymers that areelectronically insulating. In such cases, the redox active slurry may ormay not contain an additional carrier liquid. Additives can be combinedwith the condensed phase liquid redox compound to increase electronicconductivity. In some embodiments, such electronically insulatingorganic redox compounds are rendered electrochemically active by mixingor blending with particulates of an electronically conductive material,such as solid inorganic conductive materials including but not limitedto metals, metal carbides, metal nitrides, metal oxides, and allotropesof carbon including carbon black, graphitic carbon, carbon fibers,carbon microfibers, vapor-grown carbon fibers (VGCF), fullerenic carbonsincluding “buckyballs”, carbon nanotubes (CNTs), multiwall carbonnanotubes (MWNTs), single wall carbon nanotubes (SWNTs), graphene sheetsor aggregates of graphene sheets, and materials comprising fullerenicfragments.

In some embodiments, such electronically insulating organic redoxcompounds are rendered electronically active by mixing or blending withan electronically conductive polymer, including but not limited topolyaniline or polyacetylene based conductive polymers orpoly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole, polythiophene,poly(p-phenylene), poly(triphenylene), polyazulene, polyfluorene,polynaphtalene, polyanthracene, polyfuran, polycarbazole,tetrathiafulvalene-substituted polystyrene, ferrocene-substitutedpolyethylene, carbazole-substituted polyethylene, polyoxyphenazine,polyacenes, or poly(heteroacenes. The conductive additives form anelectrically conducting framework within the insulating liquid redoxcompounds that significantly increases the electrically conductivity ofthe composition. In some embodiments, the conductive addition forms apercolative pathway to the current collector. In some embodiments theredox-active electrode material comprises a sol or gel, including forexample metal oxide sols or gels produced by the hydrolysis of metalalkoxides, amongst other methods generally known as “sol-gelprocessing,” Vanadium oxide gels of composition V_(x)O_(y) are amongstsuch redox-active sol-gel materials.

Other suitable positive active materials for use in the cathode 140include solid compounds known to those skilled in the art as those usedin NiMH (Nickel-Metal Hydride) or Nickel Cadmium (NiCd) batteries. Stillother positive electrode compounds for Li storage include those used incarbon monofluoride batteries, generally referred to as CFx, or metalfluoride compounds having approximate stoichiometry MF₂ or MF₃ where Mcomprises, for example, Fe, Bi, Ni, Co, Ti, or V. Examples include thosedescribed in H. Li, P. Balaya, and J. Maier, Li-Storage viaHeterogeneous Reaction in Selected Binary Metal Fluorides and Oxides,Journal of The Electrochemical Society, 151 [11] A1878-A1885 (2004), M.Bervas, A. N. Mansour, W.-S. Woon, J. F. Al-Sharab, F. Badway, F.Cosandey, L. C. Klein, and G. G. Amatucci, “Investigation of theLithiation and Delithiation Conversion Mechanisms in a Bismuth FluorideNanocomposites”, J. Electrochem. Soc., 153, A799 (2006), and I. Plitz,F. Badway, J. Al-Sharab, A. DuPasquier, F. Cosandey and G. G. Amatucci,“Structure and Electrochemistry of Carbon-Metal Fluoride NanocompositesFabricated by a Solid State Redox Conversion Reaction”, J. Electrochem.Soc., 152, A307 (2005).

As another example, fullerenic carbon including single-wall carbonnanotubes (SWNTs), multiwall carbon nanotubes (MWNTs), or metal ormetalloid nanowires may be used as ion-storage materials. One example isthe silicon nanowires used as a high energy density storage material ina report by C. K. Chan, H. Peng, G. Liu, K. McIlwrath, X. F. Zhang, R.A. Huggins, and Y. Cui, High-performance lithium battery anodes usingsilicon nanowires, Nature Nanotechnology, published online 16 Dec. 2007;doi:10.1038/nnano.2007.411. In some embodiments, electroactive materialsfor the cathode 140 in a lithium system can include the general familyof ordered rocksalt compounds LiMO₂ including those having the α-NaFeO₂(so-called “layered compounds”) or orthorhombic-LiMnO₂) structure typeor their derivatives of different crystal symmetry, atomic ordering, orpartial substitution for the metals or oxygen. M comprises at least onefirst-row transition metal but may include non-transition metalsincluding but not limited to Al, Ca, Mg, or Zr. Examples of suchcompounds include LiCoO₂, LiCoO₂ doped with Mg, LiNiO₂, Li(Ni, Co, Al)O₂(known as “NCA”) and Li(Ni, Mn, Co)O₂ (known as “NMC”). Other familiesof exemplary cathode 140 electroactive materials includes those ofspinel structure, such as LiMn₂O₄ and its derivatives, so-called“layered-spinel nanocomposites” in which the structure includesnanoscopic regions having ordered rocksalt and spinel ordering, olivinesLiMPO₄ and their derivatives, in which M comprises one or more of Mn,Fe, Co, or Ni, partially fluorinated compounds such as LiVPO₄F, other“polyanion” compounds as described below, and vanadium oxides V_(x)O_(y)including V₂O₅ and V₆O₁₁.

In some embodiments, the cathode 140 electroactive material comprises atransition metal polyanion compound, for example as described in U.S.Pat. No. 7,338,734. In some embodiments the active material comprises analkali metal transition metal oxide or phosphate, and for example, thecompound has a composition A_(x)(M′_(1−a)M″_(a))_(y)(XD₄)_(z),A_(x)(M′_(1−a)M″_(a))_(y)(DXD₄)_(z), orA_(x)(M′_(1−a)M″_(a))_(y)(X₂D₇)_(z), and have values such that x, plusy(1−a) times a formal valence or valences of M′, plus ya times a formalvalence or valence of M″, is equal to z times a formal valence of theXD₄, X₂D₇, or DXD₄ group; or a compound comprising a composition(A_(1−a)M″_(a))_(x)M′_(y)(XD₄)_(z),(A_(1−a)M″_(a))_(x)M′_(y)(DXD₄)z(A_(1−a)M″_(a))_(x)M′_(y)(X₂D₇)_(z) andhave values such that (1−a)x plus the quantity ax times the formalvalence or valences of M″ plus y times the formal valence or valences ofM′ is equal to z times the formal valence of the XD₄, X₂D₇ or DXD₄group. In the compound, A is at least one of an alkali metal andhydrogen, M′ is a first-row transition metal, X is at least one ofphosphorus, sulfur, arsenic, molybdenum, and tungsten, M″ any of a GroupIIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIBmetal, D is at least one of oxygen, nitrogen, carbon, or a halogen. Thepositive electroactive material can be an olivine structure compoundLiMPO₄, where M is one or more of V, Cr, Mn, Fe, Co, and Ni, in whichthe compound is optionally doped at the Li, M or O-sites. Deficienciesat the Li-site are compensated by the addition of a metal or metalloid,and deficiencies at the O-site are compensated by the addition of ahalogen. In some embodiments, the positive active material comprises athermally stable, transition-metal-doped lithium transition metalphosphate having the olivine structure and having the formula(Li_(1−x)Z_(x))MPO₄, where M is one or more of V, Cr, Mu, Fe, Co, andNi, and Z is a non-alkali metal dopant such as one or more of Ti, Zr,Nb, Al, or Mg, and x ranges from 0.005 to 0.05.

In other embodiments, the lithium transition metal phosphate materialhas an overall composition of Li_(1−x−z)M_(1+x)PO₄, where M comprises atleast one first row transition metal selected from the group consistingof Ti, V, Cr, Mn, Fe, Co and Ni, where x is from 0 to 1 and z can bepositive or negative. Ni includes Fe, z is between about 0.15-0.15. Thematerial can exhibit a solid solution over a composition range of0<x<0.15, or the material can exhibit a stable solid solution over acomposition range of x between 0 and at least about 0.05, or thematerial can exhibit a stable solid solution over a composition range ofx between 0 and at least about 0.07 at room temperature (22-25° C.). Thematerial may also exhibit a solid solution in the lithium-poor regime,e.g., where x≥0.8, or x≥0.9, or x≥0.95.

In some embodiments the redox-active electrode material comprises ametal salt that stores an alkali ion by undergoing a displacement orconversion reaction. Examples of such compounds include metal oxidessuch as CoO, Co₃O₄, NiO, CuO, MnO, typically used as a negativeelectrode in a lithium battery, which upon reaction with Li undergo adisplacement or conversion reaction to form a mixture of Li₂O and themetal constituent in the form of a more reduced oxide or the metallicform. Other examples include metal fluorides such as CuF₂, FeF₂, FeF₃,BiF₃, CoF₂, and NiF₂, which undergo a displacement or conversionreaction to form LiF and the reduced metal constituent. Such fluoridesmay be used as the positive electrode in a lithium battery. In otherembodiments the redox-active electrode material comprises carbonmonofluoride or its derivatives. In some embodiments the materialundergoing displacement or conversion reaction is in the form ofparticulates having on average dimensions of 100 nanometers or less. Insome embodiments the material undergoing displacement or conversionreaction comprises a nanocomposite of the active material mixed with aninactive host, including but not limited to conductive and relativelyductile compounds such as carbon, or a metal, or a metal sulfide. FeS₂and FeF₃ can also be used as cheap and electronically conductive activematerials in a nonaqueous or aqueous lithium system.

In some embodiments, the working ion is selected from the groupconsisting of Li⁺, Na⁺, Mg²⁺, Al³⁺, or Ca²⁺.

In some embodiments, the working ion is selected from the groupconsisting of Li⁺ or Na⁺.

In some embodiments, the semi-solid ion-storing redox compositionincludes a solid including an ion-storage compound.

In some embodiments, the ion is proton or hydroxyl ion and the ionstorage compound includes those used in a nickel-cadmium or nickel metalhydride battery.

In some embodiments, the ion is lithium and the ion storage compound isselected from the group consisting of metal fluorides such as CuF₂,FeF₂, FeF₃, BiF₃, CoF₂, and NiF₂.

In some embodiments, the ion is lithium and the ion storage compound isselected from the group consisting of metal oxides such as CoO, Co₃O₄,NiO, CuO, MnO.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from compounds with formulaLi_(1−x)Z_(x))MPO₄, where M is one or more of V, Cr, Mn, Fe, Co, and Ni,and Z is a non-alkali metal dopant such as one or more of Ti, Zr, Nb,Al, or Mg, and x ranges from 0.005 to 0.05.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from compounds with formulaLiMPO₄, where M is one or more of V, Cr, Mn. Fe, Co, and Ni, in whichthe compound is optionally doped at the Li, M or O-sites.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from the group consisting ofA_(x)(M′_(1−a)M″_(a))_(y)(XD₄)_(z), A_(x)(M′_(1−a)M″_(a))_(y)(DXD₄)_(z),and A_(x)(M′_(1−a)M″_(a))_(y)(X₂D₇)_(z), wherein x, plus y(1−a) times aformal valence or valences of M′, plus ya times a formal valence orvalence of M″, is equal to z times a formal valence of the XD₄, X₂D₇, orDXD₄ group; and A is at least one of an alkali metal and hydrogen, M′ isa first-row transition metal, X is at least one of phosphorus, sulfur,arsenic, molybdenum, and tungsten, M″ any of a Group IIA, IIIA, IVA, VA,VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIB metal, D is at leastone of oxygen, nitrogen, carbon, or a halogen.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from the group consisting ofA_(1−a)M″_(a))_(x)M′_(y)(XD₄)_(z), (A_(1−a)M″_(a))_(x)M′_(y)(DXD₄)z andA_(1−a)M″_(a))_(x)M′_(y)(X₂D₇)_(z), where (1−a)x plus the quantity axtimes the formal valence or valences of M″ plus y times the formalvalence or valences of M′ is equal to z times the formal valence of theXD₄, X₂D₇ or DXD₄ group, and A is at least one of an alkali metal andhydrogen, M′ is a first-row transition metal, X is at least one ofphosphorus, sulfur, arsenic, molybdenum, and tungsten, M″ any of a GroupIIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIBmetal, D is at least one of oxygen, nitrogen, carbon, or a halogen.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from the group consisting ofordered rocksalt compounds LiMO₂ including those having the includingthose having the α-NaFeO₂ and orthorhombic LiMnO₂ structure type ortheir derivatives of different crystal symmetry, atomic ordering, orpartial substitution for the metals or oxygen, where M includes at leastone first-row transition metal but may include non-transition metalsincluding but not limited to Al, Ca, Mg or Zr.

In some embodiments, the semi-solid ion storing redox compositionincludes a solid including amorphous carbon, disordered carbon,graphitic carbon, or a metal-coated or metal decorated carbon.

In some embodiments, the semi-solid ion storing redox composition caninclude a solid including nanostructures, e.g., nanowires, nanorods, andnanotetrapods.

In some embodiments, the semi-solid ion storing redox compositionincludes a solid including an organic redox compound.

In some embodiments, the positive electrode can include a semi-solid ionstoring redox composition including a solid selected from the groupsconsisting of ordered rocksalt compounds LiMO₂ including those havingthe α-NaFeO₂ and orthorhombic-LiMnO₂ structure type or their derivativesof different crystal symmetry, atomic ordering, or partial substitutionfor the metals or oxygen, wherein M Includes at least one first-rowtransition metal but may include non-transition metals including but notlimited to Al, Ca, Mg, or Zr. The negative electrode can includes asemi-solid ion-storing composition including a solid selected from thegroup consisting of amorphous carbon, disordered carbon, graphiticcarbon, or a metal-coated or metal-decorated carbon.

In some embodiments, the positive electrode can include a flowablesemi-solid ion-storing redox composition including a solid selected fromthe group consisting of A_(x)(M′_(1−a)M″_(a))_(y)(XD₄)_(z),A_(x)(M′_(1−a)M″_(a))_(y)(DXD₄)_(z), andA_(x)(M′_(1−a)M″_(a))_(y)(X₂D₇)_(z), and where x, plus y(1−a) times aformal valence or valences of M′, plus ya times a formal valence orvalence of M″, is equal to z times a formal valence of the XD₄, X₂D₇, orDXD₄ group, and A is at least one of an alkali metal and hydrogen, M′ isa first-row transition metal, X is at least one of phosphorus, sulfur,arsenic, molybdenum, and tungsten, M″ any of a Group IIA, IIIA, IVA, VA,VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIB metal, D is at leastone of oxygen, nitrogen, carbon, or a halogen and the negative electrodeincludes a flowable semi-solid ion-storing redox composition including asolid selected from the group consisting of amorphous carbon, disorderedcarbon, graphitic carbon, or a metal-coated or metal-decorated carbon.

In some embodiments, the positive electrode can include a flowablesemi-solid ion-storing redox composition including a compound with aspinel structure.

In some embodiments, the positive electrode includes a flowablesemi-solid ion-storing redox composition including a compound selectedfrom the group consisting of LiMn₂O₄ and its derivatives; layered-spinelnanocomposites in which the structure includes nanoscopic regions havingordered rocksalt and spinel ordering; so-called “high voltage spinels”with a potential vs. Li/Li+ that exceeds 4.3V including but not limitedto LiNi0.5Mn1.5O4, olivines LiMPO₄ and their derivatives, in which Mincludes one or more of Mn, Fe, Co, or Ni, partially fluorinatedcompounds such as LiVOP₄F, other “polyanion” compounds, and vanadiumoxides V_(x)O_(y) including V₂O₅ and V₆O₁₁.

In some embodiments the semi-solid battery is a lithium battery, and theanode 150 compound comprises graphite, graphitic or non-graphiticcarbon, amorphous carbon, mesocarbon microbeads, boron-carbon alloys,hard or disordered carbon, lithium titanate spinel, or a solid metal ormetal alloy or metalloid or metalloid alloy that reacts with lithium toform intermetallic compounds, e.g., Si, Ge, Sn, Bi, Zn, Ag, Al, anyother suitable metal alloy, metalloid alloy or combination thereof. Moreparticularly the metals, metal alloys, or metalloids are selected from agroup that has a high capacity for intercalating lithium such as, forexample, silicon, bismuth, barium, gallium, indium, zinc, tin, antimony,aluminum, gold, titanium oxide, molybdenum, germanium, manganese,niobium, vanadium, tantalum, iron, copper, chromium, nickel, cobalt,zirconium, yttrium, molybdenum oxide, germanium oxide, silicon oxide,silicon carbide, or a lithiated metal or metal alloy including, suchcompounds as LiAl, Li₉Al₄, Li₃Al, LiZn, LiAg, Li₁₀Ag₃, Li₅B₄, Li₇B₆,Li₁₂Si₇, Li₁₂Si₇, Li₂₁Si₈, Li₁₃Si₄, Li₂₁Si₅, Li₅Sn₂, Li₁₃Sn₅, Li₇Sn₂,Li₂₂Sn₅, Li₂Sb, Li₃Sb, LiBi, or Li₃Bi, or amorphous metal alloys oflithiated or non-lithiated compositions, any other high capacitymaterials or alloys thereof, or any other combination thereof. In someembodiments, the high capacity material in the anode 150 can result inthe anode 150 having a capacity in the range of about 700 mAh/g to about1,200 mAh/g.

In some embodiments, the electrochemical function of the semi-solidredox cell is improved by mixing or blending the cathode 140 and/oranode 150 particles with particulates of an electronically conductivematerial, such as solid inorganic conductive materials including but notlimited to metals, metal carbides, metal nitrides, metal oxides, andallotropes of carbon including carbon black, graphitic carbon, carbonfibers, carbon microfibers, vapor-grown carbon fibers (VGCF), fullereniccarbons including “buckyballs”, carbon nanotubes (CNTs), multiwallcarbon nanotubes (MWNTs), single wall carbon nanotubes (SWNTs), graphenesheets or aggregates of graphene sheets, and materials comprisingfullerenic fragments. In some embodiments, such electronicallyinsulating organic redox compounds are rendered electronically active bymixing or blending with an electronically conductive polymer, includingbut not limited to polyaniline or polyacetylene based conductivepolymers or poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole,polythiophene, poly(p-phenylene), poly(triphenylene), polyazulene,polyfluorene, polynaphtalene, polyanthracene, polyfuran, polycarbazole,tetrathiafulvalene-substituted polystyrene, ferrocene-substitutedpolyethylene, carbazole-substituted polyethylene, polyoxyphenazine,polyacenes, or poly(heteroacenes).). In some embodiments, the resultingcathode or anode mixture has an electronic conductivity of at leastabout 10⁻⁶ S/cm. In other embodiments, the mixture has an electronicconductivity between approximately 10⁻⁶ S/cm and 10⁻³ S/cm. In otherembodiments, the mixture has an electronic conductivity of at leastabout 10⁻⁵ S/cm, or at least about 10⁻⁴ S/cm, of at least about 10⁻³S/cm, of at least about 10⁻² S/cm or more.

In some embodiments, the particles included in the semi-solid anode orcathode can be configured to have a partial or full conductive coating.

In some embodiments, the semi-solid ion-storing redox compositionincludes an ion-storing solid coated with a conductive coating material.In some embodiments, the conductive coating material has higher electronconductivity than the solid. In some embodiments, the solid is graphiteand the conductive coating material is a metal, metal carbide, metaloxide, metal nitride, or carbon. In some embodiments, the metal iscopper.

In some embodiments, the solid of the semi-solid ion-storing material iscoated with metal that is redox inert at the operating conditions of theredox energy storage device. In some embodiments, the solid of thesemi-solid ion storing material is coated with copper to increase theconductivity of the storage material particle, to increase the netconductivity of the semi-solid, and/or to facilitate charge transferbetween energy storage particles and conductive additives. In someembodiments, the storage material particle is coated with, about 1.5% byweight metallic copper. In some embodiments, the storage materialparticle is coated with about 3.0% by weight metallic copper. In someembodiments, the storage material particle is coated with about 8.5% byweight metallic copper. In some embodiments, the storage materialparticle is coated with about 10.0% by weight metallic copper. In someembodiments, the storage material particle is coated with about 15.0% byweight metallic copper. In some embodiments, the storage materialparticle is coated with about 20.0% by weight metallic copper.

In some embodiments, the conductive coating is placed on the cathode 140and/or anode 150 particles by chemical precipitation of the conductiveelement and subsequent drying and/or calcination.

In some embodiments, the conductive coating is placed on the cathode 140and/or anode 150 particles by electroplating (e.g., within a fluidizedbed).

In some embodiments, the conductive coating is placed on the cathode 140and/or anode 150 particles by co-sintering with a conductive compoundand subsequent comminution.

In some embodiments, the electrochemically active particles have acontinuous intraparticle conductive material or are embedded in aconductive matrix.

In some embodiments, a conductive coating and intraparticulateconductive network is produced by multicomponent-spray-drying, asemi-solid cathode 140 and/or anode 150 particles and conductivematerial particulates.

In some embodiments, the semi-solid composition also includes conductivepolymers that provide an electronically conductive element. In someembodiments, the conductive polymers are one or more of a polyacetylene,olythiophene, polypyrrole, poly(p-phenylene), poly(triphenylene),polyazulene, polyfluorene, polynaphtalene, polyanthracene, polyfuran,polycarbazole, polyacenes, poly(heteroacenes). In some embodiments, theconductive polymer is a compound that reacts in-situ to form aconductive polymer on the surface of the active material particles. Insome embodiments, the compound can be 2-hexylthiophene or3-hexylthiophene and oxidizes during charging of the battery to form aconductive polymer coating on solid particles in the cathode semi-solidsuspension. In other embodiments, redox active material can be embeddedin conductive matrix. The redox active material can coat the exteriorand interior interfaces in a flocculated or agglomerated particulate ofconductive material. In some embodiments, the redox-active material andthe conductive material can be two components of a compositeparticulate. Without being bound by any theory or mode of operation,such coatings can pacify the redox active particles and can help preventundesirable reactions with carrier liquid or electrolyte. As such, itcan serve as a synthetic solid-electrolyte interphase (SEI) layer.

In some embodiments, inexpensive iron compounds such as pyrite (FeS₂)are used as inherently electronically conductive ion storage compounds.In some embodiments, the ion that is stored is Li⁺.

In some embodiments, redox mediators are added to the semi-solid toimprove the rate of charge transfer within the semi-solid electrode. Insome embodiments, this redox mediator is ferrocene or aferrocene-containing polymer. In some embodiments, the redox mediator isone or more of tetrathiafulvalene-substituted polystyrene,ferrocene-substituted polyethylene, carbazole-substituted polyethylene.

In some embodiments, the surface conductivity or charge transferresistance of current collectors 110/120 used in the semi-solid batteryis increased by coating the current collector surface with a conductivematerial. Such layers can also serve as a synthetic SEI layer.Non-limiting examples of conductive coating materials include carbon, ametal, metal-carbide, metal nitride, metal oxide, or conductive polymer.In some embodiments, the conductive polymer includes but is not limitedto polyaniline or polyacetylene based conductive polymers orpoly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole, polythiophene,poly(p-phenylene), poly(triphenylene), polyazulene, polyfluorene,polynaphtalene, polyanthracene, polyfuran, polycarbazole,tetrathiafulvalene-substituted polystyrene, ferrocene-substitutedpolyethylene, carbazole-substituted polyethylene, polyoxyphenazine,polyacenes, or poly(heteroacenes). In some embodiments, the conductivepolymer is a compound that reacts in-situ to form a conductive polymeron the surface of the current collector. In some embodiments, thecompound is 2-hexylthiophene and oxidizes at a high potential to form aconductive polymer coating on the current collector. In someembodiments; the current collector is coated with metal that isredox-inert at the operating conditions of the redox energy storagedevice.

The semi-solid redox compositions can include various additives toimprove the performance of the redox cell. The liquid phase of thesemi-solids in such instances would comprise a solvent, in which isdissolved an electrolyte salt, and binders, thickeners, or otheradditives added to improve stability, reduce gas formation, improve SEIformation on the negative electrode particles, and the like. Examples ofsuch additives included vinylene carbonate (VC), vinylethylene carbonate(VEC), fluoroethylene carbonate (FEC), or alkyl cinnamates, to provide astable passivation layer on the anode or thin passivation layer on theoxide cathode, propane sultone (PS), propene sultone (PrS), or ethylenethiocarbonate as antigassing agents, biphenyl (BP), cyclohexylbenzene,or partially hydrogenated terphenyls, as gassing/safety/cathodepolymerization agents, or lithium bis(oxatlato)borate as an anodepassivation agent.

In some embodiments, the semi-solid cathode 140 and/or anode 150 caninclude a non-aqueous liquid electrolyte that can include polar solventssuch as, for example, alcohols or aprotic organic solvents. Numerousorganic solvents have been proposed as the components of Li-ion batteryelectrolytes, notably a family of cyclic carbonate esters such asethylene carbonate, propylene carbonate, butylene carbonate, and theirchlorinated or fluorinated derivatives, and a family of acyclic dialkylcarbonate esters, such as dimethyl carbonate, diethyl carbonate,ethylmethyl carbonate, dipropyl carbonate, methyl propyl carbonate,ethyl propyl carbonate, dibutyl carbonate, butylmethyl carbonate,butylethyl carbonate and butylpropyl carbonate. Other solvents proposedas components of Li-ion battery electrolyte solutions includey-butyrolactone, dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether,sulfolane, methylsulfolane, acetonitrile, propiononitrile, ethylacetate, methyl propionate, ethyl propionate, dimethyl carbonate,tetraglyme, and the like. These nonaqueous solvents are typically usedas multicomponent mixtures, into which a salt is dissolved to provideionic conductivity. Exemplary salts to provide lithium conductivityinclude LiClO₄, LiPF₆, LiBF₄, LiTFSI, LiBETI, LiBOB, and the like.

In some embodiments, the non-aqueous cathode 140 and/or anode 150semi-solid compositions are prevented from absorbing impurity water andgenerating acid (such as HF in the case of LiPF₆ salt) by incorporating,compounds that getter water into the active material suspension, or intothe storage tanks or other plumbing of the system, for example, in thecase of redox flow cell batteries. Optionally, the additives are basicoxides that neutralize the acid. Such compounds include but are notlimited to silica gel, calcium sulfate (for example, the product knownas Drierite), aluminum oxide and aluminum hydroxide.

In some embodiment, the cathode 140 can be a semi-solid cathode and theanode 150 can be a conventional anode for example, a solid anode formedfrom the calendering process as known as is commonly known in the arts.In some embodiments, the cathode 140 can be a semi-solid cathode and theanode 150 can also be a semi-solid anode as described herein. In someembodiments, the cathode 140 and the anode 150 can both be semi-solidflowable electrodes, for example, for use in a redox flow cell.

FIG. 2 shows a schematic illustration of an electrochemical cell 200that includes a positive current collector 210, a negative currentcollector 220, and a separator 230 disposed between the positive currentcollector 210 and the negative current collector 220, Both the positivecurrent collector 210 and the negative current collector have athickness t₃ and the separator 230 has a thickness t₄. A cathode 240having a thickness t₅ is disposed between the positive current collector210 and the separator 230, and an anode 250 having a thickness t₆ isdisposed between the negative current collector 220 and the separator230.

The cathode 240 and anode 250 of the electrochemical cell 200 can beformed using a conventional coating and calendering process. Forexample, the cathode 240 and anode 250 can be manufactured by mixingelectrochemically active ion-storage compounds (active materials),electronically conductive additives, and polymeric binders with asolvent to form a slurry, coating the slurry onto metal foil currentcollectors 210 and 220, and then calendering the coated currentcollector under high pressure to increase density and control thicknessof the finished electrode. The finished electrode is then slit/cut intosizes and/or shapes that are appropriate for the form factor of themanufactured battery. The slit electrode composites can then be co-woundor co-stacked with intervening separator 230 layers to construct batterywindings, i.e. “jelly-rolls” or “stacks”, which are then packaged inmetal cans, flexible polymer pouches, etc. The resulting electrochemicalcell is then infiltrated with liquid electrolyte in a carefullycontrolled environment.

The anode 250 can be a conventional anode (e.g., carbon-based) such thatthe anode 250 and the cathode 240 can have comparable capacities suchas, for example, about 150-200 mAh/g. Thus, the thickness t₅ of thecathode 240 and the thickness t₆ of the anode 250 are substantially thesame, e.g., about 150 μm, and the capacities of the anode 240 and thecathode 250 are “matched.” The thickness t₄ of the separator 220 istypically substantially less than the thickness t₅ of the cathode 240and thickness t₆ of the anode 250 e.g., about 20 μm. The currentcollectors can be metal foils having a thickness comparable to theseparator, e.g., about 20 μm.

One significant disadvantage of the conventional electrodes used in theelectrochemical cell 200 is that the loading density of the activematerials cannot be increased to increase the capacity of theelectrodes, in part, due to manufacturing limitation of thecoating/calendering process. Increasing the thickness of the electrodesin conventional electrochemical cells beyond 150-200 μm is also notpractical because: (1) thicker electrodes made using the conventionalcoating/calendering process tend to delaminate from the currentcollectors during the high speed coating process and rolling process,and (2) thick electrodes made using the conventional coating/calenderingprocess have low conductivity, which dramatically increases the cellimpedance. To overcome these limitations, a series of cells aretypically stacked to obtain the desired capacity. This stacking of cellsresults in a significant portion of the volume of the battery to beoccupied by inactive materials, i.e., the separator 230 and currentcollectors 210 and 220. Therefore, the ratio of active to inactivematerials is low, which correlates to a significant reduction in energydensity.

For example, if the thickness t₃ of the current collectors 210 and 220is 20 μm each, and the thickness t₄ of the separator 230 is also 20 μm,the total inactive material thickness is 60 μm. If the thickness t₅ ofthe cathode 240 is 150 μm and the thickness t₆ of the anode 250 is also150 μm, the total active material thickness is 300 μm. Therefore,approximately 16% of the total thickness of the electrochemical cell 200is occupied by inactive material, which does not contribute to theenergy density and charge capacity of the battery.

One option for producing higher energy capacity is through the use ofhigh capacity active materials, Si or Sn, in the anode composition. FIG.3 shows a schematic illustration of a high capacity electrochemical cell300 that includes a positive current collector 310, a negative currentcollector 320, and a separator 330 disposed between the positive currentcollector 310 and the negative current collector 320. Both the positivecurrent collector 310 and the negative current collector 320 have athickness t₇ and the separator 330 has a thickness t₈. A cathode 340having a thickness t₉ is disposed between the positive current collector310 and the separator 330, and a high capacity anode 350 having athickness t₁₀ is disposed between the negative current collector 320 andthe separator 330.

The cathode 340 can be any conventional cathode that uses binders. Thecathode 340 can be manufactured using a conventional method as describedwith reference to FIG. 2. The thickness t₉ of the conventional cathode340 can be, for example, about 150 μm and can have a capacity, forexample, of about 150-200 mAh/g. The anode 350 is a high capacity anodethat includes a high capacity material, e.g., Si or Sn and can have anycomposition as described herein. The anode 350 can have a capacity ofabout 700-1,200 mAh/g. Although the anode 350 has a much higher capacitycompared with a conventional anode, e.g., the anode 250, the anode 350capacity has to be matched with the capacity of cathode 350. Since theconventional cathode 340 used in the electrochemical cell 300 cannothave a thickness t₉ greater than about 150-200 μm due to limitations asdescribed herein, the anode 350 has to be made thinner. For example,high capacity anode 350 can have a thickness t₁₀ of about 30-50 μm tohave a capacity that matches the capacity of the cathode 340. Coatingson the order of 30-50 μm begin to approach the thickness level of asingle graphite particle and therefore are manufactured using expensivefabrication processes, e.g., atomic layer deposition, vapor deposition,sputtering, and the likes. This limitation prevents the full utilizationof the potential energy capacity achievable with the high capacity anode350.

In order to increase the capacity of a battery, a series of individualcells 300 can be stacked, as described with reference to theelectrochemical cell 200. Although the capacity of electrochemical cells200 and 300 are substantially equivalent, more individual cells 300 canfit into a “stack” of a given form factor because the anode 350 issignificantly thinner than the anode 250. However, a significantpercentage of the finished battery is still occupied by the inactivematerials. For example, the thickness t₇ of the current collectors 310and 320 is the same as current collectors 210 and 220 (i.e., 20 μmeach), and the thickness t₈ of the separator 330 is the same as theseparator 230 (i.e., 20 μm), which represents the total inactivematerial thickness of 60 μm. If the thickness t₉ of the cathode 340 isthe same as the cathode 240 (i.e., 150 μm) and the thickness t₁₀ of thehigh capacity anode 350 is 50 μm, the total active material thickness is200 μm. Therefore, approximately 23% of the total thickness of theelectrochemical cell 300 is occupied by inactive material, which doesnot contribute to the energy density and charge capacity of the battery.Although the capacity of the finished battery in this example utilizingelectrochemical cells 300 would be greater than the capacity of thefinished battery utilizing electrochemical cells 200 because the thinneranodes 350 allow more cells 300 to fit into the same form factor, ahigher percentage (23% vs. 16%) of the finished battery is made frommaterials that are not contributing to charge capacity of the battery,thus, reducing its energy density. Said another way, while the highcapacity anode 350 enables the stacking of more electrochemical cells300 in a battery compared to the conventional anode 250 to get a highercapacity battery, the percentage of the inactive material is also higherwhich negates some of this benefit.

As described herein, increasing the thickness of the cathode and/orincreasing the active material loading in the cathode are two ways thatthe benefits of a high capacity anode can be utilized. While these arenot viable options with conventional cathodes for the reasons describedabove, various embodiments of semi-solid cathodes described herein canbe made thicker than the maximum thickness of 200 μm achievable withconventional cathodes and with loading densities that can be up to 5times higher than conventional cathodes. FIG. 4 shows a schematicillustration of an electrochemical cell 400 that includes a positivecurrent collector 410, a negative current collector 420, and a separator430 disposed between the positive current collector 410 and the negativecurrent collector 420. Both the positive current collector 410 and thenegative current collector 420 have a thickness t₁₁ and the separator430 has a thickness t₁₂. A semi-solid cathode 440 having a thickness t₁₃is disposed between the positive current collector 410 and the separator430, and a high capacity anode 450 having a thickness t₁₄ is disposedbetween the negative current collector 420 and the separator 430.

The anode 450 is a high capacity anode that can be formed usingconventional methods as described before with reference to FIG. 2 or anyother conventional method. In some embodiments, the anode 450 can be astationary semi-solid or a flowable semi-solid anode as describedherein. The cathode 440 is a semi-solid cathode that can be a stationarysemi-solid cathode or a flowable semi-solid cathode as described herein.In some embodiments, the semi-solid cathode is substantially free frombinders that are typically used in conventional calendered electrodes.In contrast to conventional cathodes, e.g., the cathodes 240 and 340,the semi-solid cathode 440 can be made thicker than 200 μm such as, forexample, thicker than 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm,600 μm, 700 μm, 800 μm, 900 μm, 1,000 μm, or 1,500 μm, and up to 2,000μm or more as described herein. In some embodiment, the cathode can beat least about two times, three times, four times, five times, or evensix times the thickness of the anode. The semi-solid cathode 440 canalso formulated to have up to five times the loading density ofconventional cathodes. The thicker cathode 440 and higher loadingdensities can be achieved with the semi-solid cathode 440 without thenegative consequences associated with thicker conventional electrodes.

The ability to substantially increase the thickness t₁₃ of thesemi-solid cathode 440 eliminates the restriction on the thickness t₁₄of the high capacity anode 450 that is imposed by the limitations of theconventional cathodes, e.g., cathode 250 and 350. The anode 450 cantherefore be made thicker to match the capacity of the thicker cathode450. For example, the anode 450 can have a thickness t₁₄ of about 70 μmto about 200 μm using conventional coating/calendering manufacturingmethods or upwards of 600 μm or even higher if a semi-solid anode isused as describe herein.

Therefore, the semi-solid cathode 440 and high capacity anode 450 of theelectrochemical cell 400 formed using formulations and methodologiesdescribed herein can allow the maximum capacity offered by the highcapacity materials of the anode 450 to be utilized in an electrochemicalcell with fewer stacks. In some embodiments, the semi-solid cathode 440and high capacity anode 450 can be used to make a single electrochemicalcell 400 without any stacking. Because stacking is not needed or thenumber of stacks in a battery using the semi-solid cathode 440 issubstantially less than the number of stacks needed in a high capacityanode and conventional cathode battery, for example electrochemical cell300, or a conventional anode, conventional cathode battery, for example,electrochemical cell 200, the ratio of active materials to inactivematerials in a cell stack formed from electrochemical cell 400, issubstantially higher than that of the electrochemical cells 200 and 300.Thus, most of the volume of the assembled battery is occupied by activecharge storing materials, which leads to increased overall chargecapacity and energy density of the battery. For example, as shown inFIG. 4, the thickness t₁₁ of the current collectors 410 and 420 is thesame as current collectors 310 and 320 (i.e., 20 μm each), and thethickness t₁₂ of the separator 430 is the same as the separator 330(i.e., 20 μm), which represents the total inactive material thickness of60 μm. If the thickness t₁₃ of the semi-solid cathode 440 is 500 μm andthe thickness t₁₄ of the high capacity anode 450 is 150 μm, the totalactive material thickness is 650 μm. Therefore, approximately 8.4% ofthe total thickness of the electrochemical cell 400 is occupied byinactive material, which does not contribute to the energy density andcharge capacity of the battery. Since the percentage of inactivematerials in the electrochemical cell 400 is approximately half thepercentage of inactive materials in the electrochemical cell 200 (16%)and approximately one-third the percentage of inactive materials in theelectrochemical cell 300 (23%), and because the full utilization of thehigh capacity anode 450 and higher loading density of the semi-solidcathode 440, the electrochemical cell 400 has a much higher energydensity than the other electrochemical cells 200 and 300.

Furthermore, by utilizing a semi-solid anode, the high capacity anode450 can also be made thicker than 150 μm and the semi-solid cathode 440can be made thicker than 500 μm to match the thicker high capacity anode450 further reducing the percentage of inactive materials, which do notcontribute to the energy density and charge capacity of the battery. Forexample, if the thickness t₁₄ of a semi-solid high capacity anode 450 is600 μm and the thickness t₁₃ of the semi-solid cathode 440 is increasedto 2,000 μm, the total active material thickness is 2,600 μm. If thethickness of the current collectors 410 and 420, and separator 430 havethe same thickness as above (i.e., of the 20 μm each), the percentage ofinactive materials is approximately only 2.2%. Therefore,electrochemical cells 400 made with the aforesaid materials and methodshave a substantially higher commercial appeal due, in part, to theirincreased, energy density and decreased cost.

While various embodiments of the system, methods and devices have beendescribed above, it should be understood that they have been presentedby way of example only, and not limitation. Where methods and stepsdescribed above indicate certain events occurring in certain order,those of ordinary skill in the art having the benefit of this disclosurewould recognize that the ordering of certain steps may be modified andsuch modification are in accordance with the variations of theinvention. Additionally, certain of the steps may be performedconcurrently in a parallel process when possible, as well as performedsequentially as described above. The embodiments have been particularlyshown and described, but it will be understood that various changes inform and details may be made.

The invention claimed is:
 1. An electrochemical cell, comprising: ananode; and a slurry cathode including an active material and aconductive material in a liquid electrolyte; and a separator disposedbetween the anode and the slurry cathode, wherein the thickness of thecathode is at least about two times the thickness of the anode.
 2. Theelectrochemical cell of claim 1, wherein the anode includes alithium-alloy-forming compound including at least one of tin, tinalloys, silicon, silicon alloys, antimony, aluminum, and titanium oxide.3. The electrochemical cell of claim 1, wherein the thickness of thecathode is in the range of about three to about six times the thicknessof the anode.
 4. The electrochemical cell of claim 1, wherein the liquidelectrolyte is a non-aqueous liquid electrolyte.
 5. The electrochemicalcell of claim 1, wherein the anode is a slurry anode including asuspension of an anode active material in a liquid electrolyte.
 6. Theelectrochemical cell of claim 5, wherein the liquid electrolyte in theslurry anode is a non-aqueous liquid electrolyte.
 7. The electrochemicalcell of claim 6, wherein the slurry anode includes about 40% to about75% by volume of an active material.
 8. The electrochemical cell ofclaim 1, wherein the cathode has a thickness in the range of about 300μm to about 600 μm.
 9. The electrochemical cell of claim 1, wherein theanode has a thickness in the range of about 60 μm to about 150 μm. 10.An electrochemical cell, comprising: a slurry cathode; an anodeincluding a high charge capacity material and having a thickness in therange of about 30 μm to about 600 μm; and a separator disposed betweenthe anode and the slurry cathode, wherein the cathode has a thickness ofat least about two times the anode thickness.
 11. The electrochemicalcell of claim 10, wherein the high charge capacity material includes atleast one of tin, tin alloys, silicon, silicon alloys, antimony,aluminum, and titanium oxide.
 12. The electrochemical cell of claim 10,wherein the thickness of the slurry cathode is at least about threetimes the thickness of the anode.
 13. The electrochemical cell of claim12, wherein the thickness of the slurry cathode is at least about fourtimes the thickness of the anode.
 14. The electrochemical cell of claim13, wherein the thickness of the slurry cathode is at least about fivetimes the thickness of the anode.
 15. The electrochemical cell of claim10, wherein the anode is a slurry anode including a suspension of ananode active material in a non-aqueous liquid electrolyte.
 16. Anelectrochemical cell, comprising: an anode; and a slurry cathodeincluding about 40% to about 75% by volume of an active material, about1% to about 6% by volume of a conductive material, and about 20% toabout 40% by volume of a non-aqueous liquid electrolyte, wherein thethickness of the slurry cathode is at least about two times thethickness of the anode.
 17. The electrochemical cell of claim 16,wherein the anode includes a high charge capacity material including atleast one of tin, tin alloys, silicon, silicon alloys, antimony,aluminum, and titanium oxide.
 18. The electrochemical cell of claim 16,wherein the anode is a slurry anode including a suspension of an anodeactive material in a non-aqueous liquid electrolyte.
 19. Theelectrochemical cell of claim 16, wherein the thickness of the cathodeis in the range of about three to about six times the thickness of theanode.
 20. The electrochemical cell of claim 16, wherein the cathode hasa thickness in the range of about 300 μm to about 600 μm and the anodehas a thickness in the range of about 60 μm to about 150 μm.